The present invention relates to coatings prepared from poly(meth)acrylic polymer(s) that contain photochromic compound(s), hereinafter referred to as photochromic poly(meth)acrylic coatings, and articles to which such coatings have been applied. More particularly, this invention relates to photochromic poly(meth)acrylic coatings which when applied to a substrate exhibit a particular Fischer microhardness and when exposed to activating light radiation exhibit improved photochromic performance properties, i.e., the formation of darker activated colors and faster rates of photochromic activation and fade. Further, this invention relates to photochromic poly(meth)acrylic coatings that meet commercially acceptable xe2x80x9ccosmeticxe2x80x9d standards for optical coatings applied to optical elements, e.g., lenses.
Photochromic compounds exhibit a reversible change in color when exposed to light radiation involving ultraviolet rays, such as the ultraviolet radiation in sunlight or the light of a mercury lamp. Various classes of photochromic compounds have been synthesized and suggested for use in applications in which a sunlight-induced reversible color change or darkening is desired. The most widely described classes of photochromic compounds are oxazines, pyrans and fulgides.
The use of photochromic compounds in combination with polymerizates of poly(meth)acrylates has been disclosed. For example, a process for producing photochromic products from a composition of radically polymerizable monomers, ultraviolet light initiators and photochromic compounds is described in International Patent Publication WO 96/37593. A photochromic composition comprising radically polymerizable monomer, from 0.001 to 0.2 weight percent of a photochromic compound and a photopolymerization initiator is disclosed in U.S. Pat. No. 5,621,017. In U.S. Pat. No. 5,776,376, a photochromic composition comprising a polymerizable monomer having at least one epoxy group, certain (meth)acrylate and di(meth)acrylate monomers and photochromic compounds is described.
A polymeric material of mono or multi-functional (meth)acrylates, which has a glass transition temperature of at least 125xc2x0 F. and a cross link density of from 2 to 8 moles per liter (M/L), is disclosed as a carrier of photochromic additives in WO 97/06944. European Patent Publication EP 846708 A2, describes a resin comprising at least two polymerizable (meth)acrylate monomers, at least one photochromic compound, an additive and polymerization initiator. The resultant polymerizate is described as having a glass transition temperature ranging from 20 to 50xc2x0 C. and a cross link density ranging from 0.5 M/L to 3 M/L. Photochromic polymeric materials prepared from ethoxylated bisphenol A dimethacrylate alone or in combination with other monomers are disclosed in WO publications 96/18926, 96/19741, 97/03373 and 97/21122.
The use of poly(meth)acrylic polymers in the preparation of non-photochromic low yellow index polymer compositions and optical lenses has been disclosed. An ophthalmic lens prepared from the polymerization of a composition comprising at least 50% by weight of an ethoxylated bisphenol A dimethacrylate type monomer having 0 to 10 ethoxy units is disclosed in U.S. Pat. Nos. 5,545,828 and 5,442,022. A high refractive index lens obtained by copolymerization of an ethoxylated bisphenol A dimethacrylate type monomer having 0 to 8 ethoxy units is described in U.S. Pat. No. 4,306,780.
The above patents and patent applications do not disclose an article comprising, in combination, a substrate and a photochromic coating applied to at least one surface of the substrate, the coating exhibiting good photochromic properties and being prepared from a composition comprising from 0.1 to 40.0 weight percent of a photochromic component, at least two difunctional (meth)acrylate monomers, each having from greater than 3 to less than 15 alkoxy units, in a specific weight ratio and a polymerization initiator. The coating is free of chain transfer agents, also referred to as cure modifiers which are typically found in polymerizable compositions used to form articles such as lenses.
In terms of photochromic properties, the herein described photochromic poly(meth)acrylic coatings color and fade at acceptable rates, and achieve a satisfactory activated colored state. The novel coatings described herein also exhibit a Fischer microhardness of from 50 to 150 Newtons per mm2. Such a hardness level enables the cured coating to be handled and coated, e.g., with an abrasion-resistant coating, without causing cosmetic defects, e.g., pits, spots, cracks, inclusions, etc.
In recent years, photochromic articles, particularly photochromic plastic materials for optical applications, have been the subject of considerable attention. In particular, photochromic ophthalmic plastic lenses have been investigated because of the weight advantage they offer, vis-à-vis, glass lenses. Moreover, photochromic transparencies for vehicles, such as cars and airplanes, have been of interest because of the potential safety features that such transparencies offer.
The use of photochromic coatings enables the preparation of photochromic plastic articles without the need to incorporate the photochromic compound(s) into a preformed plastic substrate. This avoids the need to develop special optical resin materials that may be used with photochromic compounds, and is particularly advantageous when the plastic, e.g., thermoplastic polycarbonate, does not have sufficient internal free volume to allow an incorporated photochromic material to activate. Further, use of photochromic coatings results in a more efficient utilization of photochromic compounds by avoiding losses associated with more conventional transfer methods, e.g., imbibition or permeation.
Other than in the operating examples, or where otherwise indicated, all values, such as those expressing wavelengths, quantities of ingredients, ranges or reaction conditions, used in this description and the accompanying claims are to be understood as modified in all instances by the term xe2x80x9caboutxe2x80x9d.
The Fischer microhardness of the coatings described herein range from 50 Newtons per mm2, preferably from 60, more preferably, from 70 Newtons per mm2 to 150 Newtons per mm2, preferably, to 130 and more preferably to 120 Newtons per mm2. The Fischer microhardness of these coatings may range between any combination of these values, inclusive of the recited values, e.g., from 51 to 149 Newton per mm2. The Fischer microhardness values are measured with a Fischerscope H-100 using a 100 milliNewton load, 30 load steps, 0.5 second pauses at an indentor depth of 2 xcexcm, as described in more detail in Part E of Example 19 herein.
The photochromic properties of the cured coatings of the present invention are characterized by a change in optical density (xcex94OD) after 30 seconds of at least 0.15, preferably, at least 0.17 and most preferably, at least 0.19; and a xcex94OD after 15 minutes of at least 0.50, preferably, at least 0.60, and most preferably, at least 0.70; and a bleach rate of not more than 200 seconds, preferably, not more than 190, and most preferably, not more than 180 secondsxe2x80x94all as measured at 22xc2x0 C. (72xc2x0 F.), and as described in more detail in Part G of Example 19 herein.
The aforedescribed photochromic performance properties of the poly(meth)acrylic coating of the present invention are a function of the temperature at which testing is done and the time intervals selected for determination of those properties. For example, photochromic poly(meth)acrylic coatings within the scope of this invention demonstrate in the 27xc2x0 C. (81xc2x0 F.) Photochromic Performance Test defined in Part G of Example 19, a xcex94OD of at least 0.20 after 30 seconds and at least 0.50 after eight minutes, and a Bleach rate of less than 150 seconds; preferably a xcex94OD of at least 0.22 after 30 seconds and at least 0.55 after eight minutes, and a Bleach rate of less than 145 seconds; and most preferably, a xcex94OD of at least 0.24 after 30 seconds and at least 0.60 after eight minutes, and a Bleach rate of less than 140 seconds.
Poly(meth)acrylic coatings having microhardness and photochromic performance properties within the aforestated ranges can be produced by the selection and balancing of the types and amounts of the components of the polymerizable composition used to prepare the coating matrix. For example, the specific properties of the components comprising the coating matrix that will effect the microhardness and photochromic performance properties of the poly(meth)acrylic matrix are the glass transition temperature and molecular weight of the components and the crosslink density of the resultant matrix. Generally, using components having higher glass transition temperatures and molecular weights results in coatings and polymerizates having an increased microhardness and vice versa. An increase in the number of reactive groups of a component will also cause an increase in the microhardness, provided that all of the groups are reacted. In this latter case, an increase in the number of reactive groups, i.e., crosslinking sites, increases the crosslinked density of the cured coating. It is believed however that the harder the coating or polymerizate the slower the activation and bleaching of the photochromic compound(s) contained therein.
The contribution of a particular polymerizable component, to either the hardness or softness of the cured poly(meth)acrylic coating can be readily determined by measuring the Fischer microhardness of the poly(meth)acrylic coating that is prepared using that component. The hardness-producing monomer component, as defined herein, is a component that increases the microhardness of the poly(meth)acrylic coating as its concentration increases. Similarly, the softness-producing monomer component, as defined herein, is a component that decreases the microhardness of the poly(meth)acrylic coating as its concentration increases. Examples of hardness-producing monomer components include, but are not limited to, (meth)acrylic monomers having from greater than 3 to not more than 9 alkoxy units, e.g., ethoxylated bisphenol A di(meth)acrylate with 4 ethoxy units, and poly(ethylene glycol)dimethacrylate having a number average molecular weight of 330. The softness-producing monomers include, but are not limited to, (meth)acrylic monomers having from greater than 9 to less than 15 alkoxy units, e.g., ethoxylated bisphenol A di(meth)acrylate with 10 ethoxy units, and poly(ethylene glycol)dimethacrylate having a number average molecular weight of 754.
The photochromic coating composition of the present invention may be prepared by combining from 0.1 to 40 weight percent of a photochromic component with at least two difunctional (meth)acrylate monomers, each having from greater than 3 to less than 15 alkoxy units, represented by formulae I and II in a weight ratio of I:II of from greater than 10:90 to less than 90:10, e.g., from 11:89 to 89:11.
The first difunctional monomer may be selected from the group of monomers and mixtures of monomers represented by the following general formula I: 
wherein each R1 is hydrogen or methyl, each R2 is hydrogen or C1-C2 alkyl, m and n are each a positive number, the sum of m and n being from greater than 3 and less than 15. The letter A designates a divalent linking group selected from straight or branched chain alkylene (usually containing from 1 to 8 carbon atoms), phenylene or C1-C9 alkyl substituted phenylene.
Linking group A may also be a group represented by the following graphic formula: 
wherein, each R3 is C1-C4 alkyl, chlorine or bromine, p and q are each an integer from 0 to 4, 
represents a divalent benzene group or a divalent cyclohexane group and X is O, S, xe2x80x94S(O2)xe2x80x94, xe2x80x94C(O)xe2x80x94, xe2x80x94CH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CH3)(C6H5)xe2x80x94 or 
is the divalent benzene group, and X is O, S, xe2x80x94CH2xe2x80x94, or xe2x80x94C(CH3)2xe2x80x94 when 
is the divalent cyclohexane group.
The second monomer may be selected from the group of monomers and mixtures of monomers represented by the following general formula II: 
wherein each R1 is hydrogen or methyl, x, y and z are each a number between 0 and less than 15 and the sum of x, y and z is greater than 3 and less than 15. The group, xe2x80x94(C2H4O)xxe2x80x94, represents poly(ethylene oxide); xe2x80x94(C3H6O)yxe2x80x94 represents poly(propylene oxide); and xe2x80x94(C4H8O)zxe2x80x94 represents poly(butylene oxide). When used in combination, the poly(ethylene oxide), poly(propylene oxide) and poly(butylene oxide) groups may be in a random or block order within the second monomer. The sum of x, y and z may be any number that falls within the range of greater than 3 and less than 15, e.g., 4, 5, 6 . . . 14. This sum may also range from any lower number to any higher number within the range of greater than 3 and less than 15, e.g., from 6 to 10, and from 11 to 14. The numbers for x, y, and z are average values and can be partial numbers, e.g., 3.1 or 14.9.
Preferably, the coating comprises two difunctional (meth)acrylate monomers. In the first monomer represented by general formula I, each R1 is methyl, each R2 is hydrogen and the divalent linking group A is represented by the following graphic formula: 
is the divalent benzene group, p and q are each 0, and x is xe2x80x94C(CH3)2xe2x80x94. The second monomer is represented by general formula II in which each R1 is methyl and x is a number greater than 3 and less than 15, and y and z are 0.
The weight ratio of the monomer(s) selected from the first group of monomer(s) to the monomer(s) selected from the second group of monomer(s), based on the total weight of the monomers, may range from greater that 10:90 to less than 90:10, from 20:80 to 80:20, and from 30:70 to 70:30. The weight ratio of the first monomer to the second monomer of the present invention may range between any combination of these ratios, inclusive of the recited ratios, e.g., from 40:60 to 85:15. The relative proportions of the first and second monomers are selected to achieve the desired photochromic and Fischer microhardness properties described herein.
The first monomer may be prepared by methods which are well known in the art. One such commonly used method involves a two-step process. In the first step, a polyol, e.g., 4,4xe2x80x2-isopropylidenediphenol, is reacted with an oxirane containing substance, for example ethylene oxide, propylene oxide, xcex1-butylene oxide and/or xcex2-butylene oxide to form what is commonly referred to as an ethoxylated, propoxylated and/or butoxylated polyol having hydroxy functionality. The level of alkoxylation can be controlled depending on the amount of oxirane containing substance used in the reaction. In the second step, the ethoxylated, propoxylated and/or butoxylated polyol is esterified, or transesterified, with an alpha-beta unsaturated meth(acrylic) acid or ester such as methacrylic acid, an alkyl methacrylate, acrylic acid, an alkyl acrylate, or a combination thereof. The second step results in the formation of the first monomer.
Polyols that may be used in the first step of preparing the first monomer include: straight chain alkylene glycols such as ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, or diethylene glycol, triethylene glycol; branched chain alkylene glycols such as 1,2-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol; phenylene diols such as ortho, meta and para dihydroxy benzene; alkyl substituted phenylene diols such as 2,6-dihydroxytoluene, 3-methylcatechol, 4-methylcatechol, 2-hydroxybenzyl alcohol, 3-hydroxybenzyl alcohol, 4-hydroxybenzyl alcohol, and 3,5-bis(1,1-dimethylethyl)-4-hydroxy-benzenemethanol; dihydroxybiphenyls such as 4,4xe2x80x2-dihydroxybiphenyl and 2,2xe2x80x2dihydroxybiphenyl; bisphenols such as 4,4xe2x80x2-isopropylidenediphenol; 4,4xe2x80x2-oxybisphenol; 4,4xe2x80x2-dihydroxybenzenephenone; 4,4,xe2x80x2-thiobisphenol; phenolphathlalein; bis(4-hydroxyphenyl)methane; 4,4xe2x80x2-(1,2-ethenediyl)bisphenol; and 4,4xe2x80x2-sulfonylbisphenol; halogenated bisphenols such as 4,4xe2x80x2-isopropylidenebis(2,6-dibromophenol), 4,4xe2x80x2-isoprepylidenebis(2,6-dichlorophenol) and 4,4xe2x80x2-isopropylidenebis(2,3,5,6-tetrachlorophenol); and biscyclohexanols, which can be prepared by hydrogenating the corresponding bisphenols, such as 4,4xe2x80x2-isopropylidenebiscyclohexanol; 4,4xe2x80x2-oxybiscyclohexanol; 4,4xe2x80x2-thiobiscyclohexanol; and bis(4-hydroxycyclohexanol)methane.
The second monomer is a bis[(meth)acryloyl-terminated] polyalkylene glycol monomer which is different than the first monomer. The second monomer is derived from a polyalkylene glycol precursor that results in a monomer having from greater than 3 to less than 15 alkoxy units. Preferably, the second monomer is a polyethylene glycol dimethacrylate that is derived from a polyethylene glycol precursor having a number average modular weight of from 200 to 600, inclusive of the recited range, e.g. 300, 400, 550, etc.
The coating composition of the present invention may also contain from 0 to 10 weight percent, based on the total weight of monomers, of polymerization initiator(s) selected from thermal initiators, photoinitiators or mixtures of such initiators. The coating composition of the present invention is free of chain transfer agents or cure modifiers typically used in casting compositions used to form articles such as lenses By xe2x80x9cfree ofxe2x80x9d is meant that the composition does not contain a material in an amount necessary to function as a chain transfer agent, i.e., a material that interrupts the growth of a chain of monomers by forming a new radical that may act as the starting point for a new chain. Examples of chain transfer agents include 2,4-diphenyl-4-methyl-1-pentene, dodecyl mercaptan, butyl mercaptan, diisopropenyl benzene and thiophenol.
Not being bound by any theory, it is believed that chain transfer agents are used in bulk polymerization processes of (meth)acrylates to avoid hot spots in the reaction vessel that could lead to runaway reactions resulting from the Trommsdorff effect. During the curing of the poly(meth)acrylic photochromic coating of the present invention, it is believed that this exothermic reaction assists in the rapid curing of the coating. In the curing of optical elements such as lenses in a mold, chain transfer agents are used to avoid optical distortions such as striations. In general, the prior art teaches the use of chain transfer agents for reasons that appear to be tied to the process of molding three dimensional articles, whereas the present invention deals with thin coatings.
Solvents that may be present in the coating composition are those that are necessary to dissolve and/or disperse the coating components. The minimum amount of solvent present in the coating composition is a solvating amount, i.e., an amount which is sufficient to solubilize the solid components in the coating composition. For example, the amount of solvent present may range from 10 to 80 weight percent based on the total weight of the coating composition.
Suitable solvents include, but are not limited to, the following: benzene, toluene, methyl ethyl ketone, methyl isobutyl ketone, acetone, ethanol, tetrahydrofurfuryl alcohol, propyl alcohol, propylene carbonate, N-methyl pyrrolidinone, N-vinyl pyrrolidinone, N-acetyl pyrrolidinone, N-hydroxymethyl pyrrolidinone, N-butyl pyrrolidinone, N-ethyl pyrrolidinone, N-(N-octyl) pyrrolidinone, N-(N-dodecyl) pyrrolidinone, 2-methoxyethyl ether, xylene, cyclohexane, 3-methyl cyclohexanone, ethyl acetate, butyl acetate, tetrahydrofuran, methanol, amyl propionate, methyl propionate, propylene glycol methyl ether, diethylene glycol monobutyl ether, dimethyl sulfoxide, dimethyl formamide, ethylene glycol, mono- and dialkyl ethers of ethylene glycol and their derivatives, which are sold as CELLOSOLVE industrial solvents by Union Carbide, and mixtures of such solvents.
The photochromic poly(meth)acrylic coating composition of the present invention may further comprise additional conventional ingredients which impart desired characteristics to the composition, or which are required for the process used to apply and cure the composition on the substrate or which enhance the cured coating made therefrom. Such additional ingredients may include mono-functional (meth)acrylic monomers, di-functional (meth)acrylic monomers other than those represented by formulae I and II, polyfunctional (meth)acrylic monomers, e.g. trimethylol propane triacrylate, and plasticizers at levels less than 20 weight percent, e.g. at 10 weight percent. The weight percent is based on the total weight of the monomers. The amount of these materials used may range from 0 to less than 20 weight percent.
Other additional ingredients may include light stabilizers, heat stabilizers, mold release agents, rheology control agents, leveling agents, e.g., surfactants, free radical scavengers and adhesion promoting agents, such as the materials used in the process for producing adherent polymeric layers on polymeric substrates which are disclosed in U.S. Pat. No. 6,150,430, which disclosure is incorporated herein by reference. Other adhesion promoters which may be used include trialkoxy silanes, preferably having an alkoxy radical of 1 to 4 carbon atoms, including xcex3-glycidoxypropyltrimethoxy silane, xcex3-aminopropyltrimethoxy silane, 3,4-epoxy cyclohexylethyltrimethoxy silane, methacryloxypropyltrimethoxysilane and aminoethyltrimethoxy silane.
Photochromic components that may be utilized in the poly(meth)acrylic coating composition(s) of the present invention are organic photochromic compounds. Such compounds may be used individually or in combination with other complementary photochromic compounds. Organic photochromic compounds or substances containing same used in the coating compositions described herein have at least one activated absorption maxima within the range of between 400 and 700 nanometers; may be incorporated, e.g., dissolved or dispersed, in the (meth)acrylic composition used to prepare the photochromic coating, and color when activated to an appropriate hue.
In one embodiment the organic photochromic component comprises:
(a) at least one photochromic organic compound having a visible lambda max of from 400 nanometers to 525 nanometers; and
(b) at least one photochromic organic compound having a visible lambda max of from greater than 525 nanometers to 700 nanometers.
Examples of photochromic compounds that may be used in the poly(meth)acrylic coating composition of the present invention include benzopyrans, naphthopyrans, e.g., naphtho[1,2-b]pyrans and naphtho[2,1-b]pyrans, phenanthropyrans, quinopyrans, benzoxazines, naphthoxazines, spiro(indoline)pyridobenzoxazines and indeno-fused naphthopyrans, such as those disclosed in U.S. Pat. No. 5,645,767. Specific examples include the novel naphthopyrans of U.S. Pat. No. 5,658,501 and the complementary organic photochromic substances disclosed in that patent from column 11, line 57 through column 13, line 36. Other photochromic substances contemplated for use herein are photochromic metal-dithizonates, e.g., mercury dithizonates, which are described in, for example, U.S. Pat. No. 3,361,706; fulgides and fulgimides, e.g. the 3-furyl and 3-thienyl fulgides and fulgimides, which are described in U.S. Pat. No. 4,931,220 at column 20, line 5 through column 21, line 38, and mixtures of the aforementioned suitable photochromic substances.
In addition, it is contemplated that a form of organic photochromic substance resistant to the effects of a polymerization initiator may also be added to the polymerizable coating composition of the present invention. Such organic photochromic substances include photochromic pigments and photochromic compounds encapsulated in metal oxides, the latter of which are described in U.S. Pat. Nos. 4,166,043 and 4,367,170.
The disclosures relating to such photochromic compounds in the aforedescribed patents are incorporated herein, in toto, by reference. The photochromic coatings of the present invention may contain a photochromic amount of one photochromic compound or a mixture of photochromic compounds, as desired. Mixtures of photochromic compounds may be used to attain certain activated colors such as a near neutral gray or brown. See, for example, U.S. Pat. No. 5,645,767, column 12, line 66 to column 13, line 19.
As used herein and in the claims, by xe2x80x9cphotochromic amountxe2x80x9d is meant that amount of organic photochromic substance which is at least sufficient to produce a photochromic effect discernible to the naked eye upon activation. The particular amount used depends often upon the intensity of color desired upon irradiation thereof. Typically, the more photochromic substance present in the polymerizable composition of the present invention or that which is incorporated into a polymerizate of the present invention, the greater the color intensity of the resulting photochromic article.
The amount of photochromic substance used in the coating or polymerizate of the present invention may be from 0.1 to 40.0 weight percent, based on the total weight of monomers. The relative amounts of the aforesaid photochromic compounds used will vary and depend in part upon the relative intensities of the color of the activated species of such compounds, and the ultimate color desired. Preferably, the concentration of photochromic substances ranges from 1.0 to 30 weight percent, more preferably, from 3 to 20 weight percent, and most preferably, from 5 to 15 weight percent, e.g., from 7 to 14 weight percent. The amount of photochromic substance in the coating or polymerizate may range between any combination of these values, inclusive of the recited range, e.g. from 0.15 to 39.9 weight percent.
The photochromic compound(s) described herein may be incorporated into the coating composition by addition to the coating composition and/or by dissolving it in solvent before adding it to the coating composition. Alternatively, although less preferred the photochromic compound(s) may be incorporated into the cured coating or polymerizate by imbibition, permeation or other transfer methods, which methods are known to those skilled in the art.
Compatible (chemically and color-wise) tints, i.e., dyes, may be added to the coating composition, applied to the coated article or applied to the substrate prior to coating to achieve a more aesthetic result, for medical reasons, or for reasons of fashion. The particular dye selected will vary and depend on the aforesaid need and result to be achieved. In one embodiment, the dye may be selected to complement the color resulting from the activated photochromic substances, e.g., to achieve a more neutral color or absorb a particular wavelength of incident light. In another embodiment, the dye may be selected to provide a desired hue to the substrate and/or coated article when the photochromic substance is in an unactivated state.
Adjuvant materials may also be incorporated into the coating composition with the photochromic substances, prior to, simultaneously with or subsequent to application or incorporation of the photochromic substances in the coating composition or cured coating. For example, ultraviolet light absorbers may be admixed with photochromic substances before their addition to the coating composition or such absorbers may be superposed, e.g., superimposed, as a layer between the photochromic coating and the incident light. Further, stabilizers may be admixed with the photochromic substances prior to their addition to the coating composition to improve the light fatigue resistance of the photochromic substances. Stabilizers, such as hindered amine light stabilizers (HALS), antioxidants, e.g., polyphenolic antioxidants, asymmetric diaryloxalamide (oxanilide) compounds and singlet oxygen quenchers, e.g., a nickel ion complex with an organic ligand, or mixtures of stabilizers are contemplated. They may be used alone or in combination. Such stabilizers are described in U.S. Pat. Nos. 4,720,356, 5,391,327 and 5,770,115, which patents are incorporated herein by reference.
The coating compositions of the present invention may be applied to substrates, of any type such as, for example paper, glass, ceramics, wood, masonry, textiles, metals and polymeric organic materials. Preferably, the substrate is a polymeric organic material, particularly, thermoset and thermoplastic polymeric organic materials, e.g., thermoplastic polycarbonate type polymers and thermoset polycarbonates such as homopolymers or copolymers of diethylene glycol bis(allyl carbonate), which are used as organic optical materials.
The amount of the coating composition applied to at least one surface of the substrate is an amount necessary to provide a sufficient quantity of the organic photochromic substance(s) to produce a coating that exhibits the required change in optical density (xcex94OD) when the cured coating is exposed to UV radiation. The required change in optical density is that which, when tested at 22xc2x0 C. (72xc2x0 F.), produces a xcex94OD of at least 0.15 after 30 seconds and at least 0.50 after 15 minutes. The bleach rate of the photochromic coating (the photochromic(s) in the coating) should be 200 seconds or less using the photochromic response testing method described in more detail in Part G of Example 19 herein. The applied coating may have a thickness of at least 1 micron, e.g. 5 microns, preferably, at least 10 microns, more preferably, at least 20 microns, e.g., 25 microns. The applied coating will also usually have a thickness of not more than 200 microns, preferably not more than 100 microns, and more preferably not more than 50 microns, e.g., 40 microns. The thickness of the coating may range between any combination of these values, inclusive of the recited values, e.g., from 1 to 200 microns.
Prior to applying the coating composition, it is typical to treat the surface of the substrate for the purposes of cleaning it and for promoting adhesion. Effective treatment techniques for plastics, such as those prepared from CR-39(copyright) diethylene glycol bis(allyl carbonate) monomer or thermoplastic polycarbonate, e.g., a resin derived from bisphenol A and phosgene, include ultrasonic cleaning; washing with an aqueous mixture of organic solvent, e.g., a 50:50 mixture of isopropanol: water or ethanol: water; UV treatment; activated gas treatment, e.g., treatment with low temperature plasma or corona discharge, and chemical treatment such as hydroxylation, i.e., etching of the surface with an aqueous solution of alkali, e.g., sodium hydroxide or potassium hydroxide, that may also contain a fluorosurfactant. See U.S. Pat. No. 3,971,872, column 3, lines 13 to 25; U.S. Pat. No. 4,904,525, column 6, lines 10 to 48; and U.S. Pat. No. 5,104,692, column 13, lines 10 to 59, which describe surface treatments of polymeric organic materials.
The treatment used for cleaning glass surfaces, e.g., ophthalmic lenses, will depend on the type of dirt present on the glass surface. Such treatments are known to those skilled in the art. For example, washing the glass with an aqueous solution that may contain a low foaming, easily rinsed detergent, followed by rinsing and drying with a lint-free cloth; and ultrasonic bath treatment in heated (about 50xc2x0 C.) wash water, followed by rinsing and drying. Pre-cleaning with an alcohol-based cleaner or organic solvent prior to washing may be required to remove adhesives from labels or tapes.
In some cases, it may be necessary to apply a primer to the surface of the substrate before application of the coating composition of the present invention. The primer serves as a barrier coating to prevent interaction of the coating ingredients with the substrate and vice versa, and/or as an adhesive layer to adhere the coating composition to the substrate. Application of the primer may be by any of the methods used in coating technology such as, for example, spray coating, spin coating, spread coating, curtain coating, dip coating, casting or roll-coating.
The use of protective coatings, some of which may contain polymer-forming organosilanes, as primers to improve adhesion of subsequently applied coatings has been described. The use of non-tintable coatings as a primer is preferred. Examples of commercial coating products that may be used include, but are not limited to, SILVUE(copyright) 124 and HI-GARD(copyright) coatings, available from SDC Coatings, Inc. and PPG Industries, Inc., respectively. In addition, depending on the intended use of the coated article, it may be necessary to apply an appropriate protective coating(s), i.e., an abrasion resistant coating onto the exposed surface of the coating composition to prevent scratches from the effects of friction and abrasion. In some cases, the primer and protective coatings are interchangeable, i.e., the same coating may be used as the primer and the protective coating(s). Other coatings or surface treatments, e.g., a tintable coating, antireflective surface, etc., may also be applied to the cured coating of the present invention.
The coating composition of the present invention may be applied using the same methods described herein for applying the primer and the protective coating(s) or other methods known in the art can be used. The coating composition may be applied by spin coating, curtain coating, dip coating, spray coating or by methods used in preparing overlays. Such methods are described in U.S. Pat. No. 4,873,029, which disclosure is incorporated herein by reference.
Following application of the coating composition to the treated surface of the substrate, the coating is cured. Depending on the substrate and monomer components selected for the coating composition of the present invention, the coating may be cured by thermal polymerization, e.g. at temperatures ranging from 22xc2x0 C. to 200xc2x0 C., by photopolymerization or by a combination of the two methods. If heating is required to obtain a cured coating, temperatures of between 80xc2x0 C. and a temperature above which the substrate is damaged due to heating, e.g., from 80xc2x0 C. to 200xc2x0 C., are typically used. For example, certain organic polymeric materials may be heated up to 130xc2x0 C. for a period of 1 to 16 hours in order to cure the coating without causing damage to the substrate. While a range of temperatures has been described for thermally curing the coated substrate, it will be recognized by persons skilled in the art that temperatures other than those disclosed herein may be used. Curing of the photochromic poly(meth)acrylic coating composition may be accomplished by irradiating the coating with ultraviolet and/or visible light so as to initiate the polymerization reaction of the polymerizable components in the coating followed by a heating step.
Polymerization of the polymerizable components in the coating may be done by including in the composition an initiating amount of material capable of generating free radicals, such as organic peroxy compounds or azobis(organonitrile) compounds, i.e., an initiator. Preferably, the initiator is used in the least amount necessary to start the curing process. Generally, the curing process is more efficient in the absence of oxygen, for example, in the presence of nitrogen, as a greater amount of initiator is required in the presence of oxygen. Methods for polymerizing compositions comprised of monomers, having ethylenically unsaturated groups which are radically polymerizable, are well known to the skilled artisan and any of those well known techniques may be used to polymerize the aforedescribed polymerizable organic compositions. Such polymerization methods include thermal polymerization, photopolymerization or a combination thereof.
Examples of suitable organic peroxy compounds, that may be used as thermal polymerization initiators include: peroxymonocarbonate esters, such as tertiarybutylperoxy isopropyl carbonate; peroxydicarbonate esters, such as di(2-ethylhexyl) peroxydicarbonate, di(secondary butyl) peroxydicarbonate and diisopropylperoxydicarbonate; diacylperoxides, such as 2,4-dichlorobenzoyl peroxide, isobutyryl peroxide, decanoyl peroxide, lauroyl peroxide, propionyl peroxide, acetyl peroxide, benzoyl peroxide, p-chlorobenzoyl peroxide; peroxyesters such as t-butylperoxy pivalate, t-butylperoxy octylate, and t-butylperoxyisobutyrate; methylethylketone peroxide, and acetylcyclohexane sulfonyl peroxide. Preferred thermal initiators are those that do not discolor the resulting coating or polymerizate.
Examples of suitable azobis(organonitrile) compounds, that may be used as thermal polymerization initiators include: azobis(isobutyronitrile), 2,2xe2x80x2-azobis(2,4-dimethylpentanenitrile), 1,1xe2x80x2-azobiscyclohexanecarbonitrile and azobis(2,4-dimethylvaleronitrile) or mixtures of such initiators. Preferably, the thermal initiator is 2,2xe2x80x2-azobis(2,4-dimethylpentanenitrile, 1,1xe2x80x2-azobiscyclohexanecarbonitrile or mixtures thereof.
The amount of thermal polymerization initiator used to initiate and polymerize the polymerizable components in the coating composition of the present invention may vary and will depend on the particular initiator used. Only that amount that is required to initiate and sustain the polymerization reaction is required, i.e., an initiating amount. With respect to the preferred azobis(organonitrile) compounds, between 0.01 and 5.0 parts of that initiator per 100 parts of the polymerizable organic composition (phm) may be used. More usually, between 0.05 and 3.0 phm is used to initiate the polymerization. Typically, the thermal cure cycle involves heating the polymerizable organic composition in the presence of the initiator from room temperature to 85xc2x0 C. to 125xc2x0 C. over a period of from 2 to 20 minutes for a coating and from 2 hours to 30 hours for a polymerizate.
Photopolymerization of the polymerizable components in the coating may be carried out in the presence of a photoinitiator using ultraviolet light and/or visible light. Photoinitiators, which are free radical initiators, are classified in two major groups based upon a mode of action. Cleavage-type photoinitiators include acetophenones, xcex1-aminoalkylphenones, benzoin ethers, benzoyl oximes, acylphosphine oxides and bisacylphosphine oxides and mixtures of such initiators. Abstraction-type photoinitiators include benzophenone, Michler""s ketone, thioxanthone, anthraquinone, camphorquinone, fluorone, ketocoumarin and mixtures of such initiators. Abstraction-type photoinitiators function better in the presence of materials such as amines and other hydrogen donor materials added to provide labile hydrogen atoms for abstraction. Typical hydrogen donors have an active hydrogen positioned alpha to an oxygen or nitrogen, e.g., alcohols, ethers and tertiary amines, or an active hydrogen atom directly attached to sulfur, e.g., thiols. In the absence of such added materials, photoinitiation may still occur via hydrogen abstraction from monomers, oligomers or other components of the system.
Cationic photoinitiators may also be used in conjunction with the aforementioned photoinitiators. Preferably, cationic initiators are used with abstraction type photoinitiators, hydrogen donor materials such as butyryl choline triphenylbutyl borate, or combinations of such materials. The preferred cationic photoinitiators are onium salts described in U.S. Pat. No. 5,639,802, column 8, line 59 to column 10, line 46, which disclosure is incorporated herein by reference. Examples of such initiators include 4,4xe2x80x2-dimethyldiphenyliodonium tetrafluoroborate, phenyl-4-octyloxyphenyl phenyliodonium hexafluoroantimonate, dodecyldiphenyl iodonium hexafluoroantimonate, [4-[(2-tetradecanol)oxy]phenyl]phenyl iodonium hexafluoroantimonate and mixtures thereof.
Examples of photopolymerization initiators which may be used include benzil, benzoin, benzoin methyl ether, benzoin isobutyl ether benzophenol, acetophenone, benzophenone, 4,4xe2x80x2-dichlorobenzophenone, 4,4xe2x80x2-bis(N,Nxe2x80x2-dimethylamino)benzophenone, diethoxyacetophenone, fluorones, e.g., the H-Nu series of initiators available from Spectra Group Limited, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-isopropylthixantone, xcex1-aminoalkylphenone, e.g., 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, acylphosphine oxides, e.g., 2,6-dimethylbenzoyldlphenyl phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, and 2,6-dimethoxybenzoyldiphenylphosphine oxide, bisacylphosphine oxides, e.g., bis(2,6-dimethyoxybenzoyl)-2,4,4-trimethylepentylphosphine oxide, bis(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, and bis(2,6-dichlorobenzoyl)-2,4,4-trimethylpentylphosphine oxide, phenyl-4-octyloxyphenyliodonium hexafluoroantimonate, dodecyldiphenyliodonium hexafluoroantimonate, (4-(2-tetradecanol)oxyphenyl)iodonium hexafluoroantimonate and mixtures thereof.
Examples of hydrogen or electron donor materials which may be utilized in combination with photoinitiators include, but are not limited to, one or more of the following: N,N-dimethyl-2,6-diisopropylanile, N-phenylglycine, ethyl-4-dimethylaminobenzoate, octyl-p-(dimethylamino)benzoate, N-methyldiethanolamine, triethanolamine, diethylethanolamine, triethylamine, diisopropylethylamine, dimethylaminomethylphenol, benzyldimethylamine, tetramethyl ammonium triphenylbutyl borate and butyryl choline triphenylbutyl borate.
The amount of photopolymerization initiator used to initiate and polymerize the polymerizable components of the coating vary and will depend on the particular initiator used. Only that amount that is required to initiate and sustain the polymerization reaction is required, i.e., an initiating amount. The photopolymerization initiator may be used in an amount from 0.01% to 5% by weight, based on the weight of monomer components.
The light source used for the photopolymerization is preferably selected from those which emit ultraviolet light and/or visible light. The light source may be a mercury lamp, a mercury lamp doped with FeI3 and/or GaI3, a germicidal lamp, a xenon lamp, a tungsten lamp, a metal halide lamp or a combination of such lamps. Typically, the absorbance spectra of the photoinitiator or photoinitiator combination is matched with the spectral output of the bulb, for example, H bulb, D bulb, Q bulb and/or V bulb for highest curing efficiency. The exposure time may vary depending upon the wavelength and intensity of the light source, the photoinitiator, and thickness of the coating. The coating of the present invention may also be cured using an electron beam process which doesn""t require the presence of an initiator.
The amount of thermal polymerization initiator and/or photopolymerization initiator and the consequent cure cycle should be adequate to produce a coating or polymerizate according to the present invention having a Fischer micro-hardness of from 50 to 150 Newtons per mm2 and the desired photochromic properties of a xcex94OD after 30 seconds of at least 0.15, after 15 minutes of at least 0.50 and a bleach rate of not more than 200 secondsxe2x80x94all as measured in the 22xc2x0 C. (72xc2x0 F.) Photochromic Performance Test described herein.
Desirably, the resulting cured coating meets commercially acceptable xe2x80x9ccosmeticxe2x80x9d standards for optical coatings. Examples of cosmetic defects of coated lens include pits, spots, inclusions, cracks and crazing of the coating. Most preferably, the coatings prepared using the photochromic coating composition of the present invention are substantially free of cosmetic defects.
Examples of polymeric organic materials that may be substrates for the coating composition of the present invention are polymers, i.e., homopolymers and copolymers, of the monomers and mixtures of monomers disclosed in U. S. Pat. No. 5,658,501 from column 15, line 28 to column 16, line 17, which is incorporated herein by reference.
Examples of such monomers and polymers include: polyol(allyl carbonate)monomers, e.g., diethylene glycol bis(allyl carbonate), which monomer is sold under the trademark CR-39; polyol(meth)acryloyl terminated carbonate monomer; diethylene glycol dimethacrylate monomers; ethoxylated phenol methacrylate monomers; diisopropenyl benzene monomers; ethoxylated trimethylol propane triacrylate monomers; ethylene glycol bismethacrylate monomers; poly(ethylene glycol)bis methacrylate monomers; urethane acrylate monomers; poly(ethoxylated bisphenol A dimethacrylate); poly(vinyl acetate); poly(vinyl alcohol); poly(vinyl chloride); poly(vinylidene chloride); polyurethanes, polythiourethanes, thermoplastic polycarbonates, such as the carbonate-linked resin derived from bisphenol A and phosgene, which is sold under the trademark LEXAN; polyesters, such as the material sold under the trademark MYLAR; poly(ethylene terephthalate); polyvinyl butyral; and poly(methyl methacrylate), such as the material sold under the trademark PLEXIGLAS and mixtures thereof.
One particularly contemplated embodiment, is the use of the combination of the photochromic poly(meth)acrylic coating composition of the present invention with polymeric organic materials such as optically clear polymerizates, i.e., materials suitable for optical applications, such as optical elements, e.g., plano and vision correcting ophthalmic lenses, windows, clear polymeric films, automotive transparencies, e.g., windshields, aircraft transparencies, plastic sheeting, etc. Such optically clear polymerizates may have a refractive index that may range from about 1.48 to about 2.00, e.g., from about 1.495 to about 1.75. Specifically contemplated are optical elements made of thermoplastic polycarbonates and thermoset polycarbonates. Application of the photochromic poly(meth)acrylic coating composition of the present invention to a polymeric film in the form of an xe2x80x9cappliquexe2x80x9d may be accomplished using the methods describe in column 17, line 28 to column 18, line 57 of U.S. Pat. No. 5,198,267.
Another particularly contemplated embodiment, is the use of the combination of the photochromic poly(meth)acrylic coating composition of the present invention with optical elements to produce photochromic optical articles. Such articles may be prepared by sequentially applying, e.g., by spraying, to the optical element a primer, the photochromic poly(meth)acrylic composition of the present invention and appropriate protective coating(s). The resulting cured coating preferably meets commercially acceptable xe2x80x9ccosmeticxe2x80x9d standards for optical coatings, and most preferably, is substantially free of cosmetic defects.
The present invention is more particularly described in the following examples, which are intended as illustrative only, since numerous modifications and variations therein will be apparent to those skilled in the art.
The following materials were added in the order described to a suitable vessel equipped with an agitator and mixed for 1 hour.
The following materials were added in the order described to a suitable vessel equipped with an agitator and mixed for 1 hour.
The following materials were added in the order described to a suitable vessel equipped with an agitator and mixed for 1 hour.
The following materials were added in the order described to a suitable vessel equipped with an agitator and mixed for 1 hour.
The following materials were added in the order described to a suitable vessel equipped with an agitator and mixed for 1 hour.
The following materials were added in the order described to a suitable vessel equipped with an agitator and mixed for 1 hour.
The following materials were added in the order described to a suitable vessel equipped with an agitator and mixed for 1 hour.